Dfrnhjy

actually i am trying to add quantity increment and decreament (+ and
- button) in minicart magento 2.3.
If anyone have any idea please guide me.

Magento 2 using KnockoutJs for render data in Minicart.
You can override template:
vendor/magento/module-checkout/view/frontend/web/template/minicart/item/default.html

And call to ajax function for update data
checkout/sidebar/updateItemQty/

Or use free module:
https://github.com/php-cuong/magento2-qty

app/design/frontend/Module/theme/Magento_Checkout/web/template/minicart/item/default.html

<div class="product-item-pricing">
 <!-- ko if: canApplyMsrp -->

 <div class="details-map">
 <span class="label" data-bind="i18n: 'Price'"></span>
 <span class="value" data-bind="i18n: 'See price before order confirmation.'"></span>
 </div>
 <!-- /ko -->
 <!-- ko ifnot: canApplyMsrp -->
 <!-- ko foreach: $parent.getRegion('priceSidebar') -->
 <!-- ko template: name: getTemplate(), data: item.product_price, as: 'price' --><!-- /ko -->
 <!-- /ko -->
 <!-- /ko -->

 <div class="details-qty qty">
 <label class="label" data-bind="i18n: 'Qty', attr: 
 for: 'cart-item-'+item_id+'-qty'"></label>
 <div class="more">+</div>
 <input data-bind="attr: 
 id: 'cart-item-'+item_id+'-qty',
 'data-cart-item': item_id,
 'data-item-qty': qty,
 'data-cart-item-id': product_sku
 , value: qty"
 type="number"
 size="4"
 class="item-qty cart-item-qty">

 <div class="less">-</div>
 <button data-bind="attr: 
 id: 'update-cart-item-'+item_id,
 'data-cart-item': item_id,
 title: $t('Update')
 "
 class="update-cart-item"
 style="display: none">
 <span data-bind="i18n: 'Update'"></span>
 </button>
 </div>
 </div>

app/design/frontend/Module/theme/Magento_Checkout/templates/cart/minicart.phtml

<script type="text/javascript">
require(["jquery"],function($){
$('body').on("click",".more, .less",function()
 var obj = $(this);
 var currentQty = obj.siblings('.cart-item-qty').val();
 var iid = obj.siblings('.update-cart-item').attr('data-cart-item');

 if(obj.hasClass('more'))
 var newAdd = parseInt(currentQty)+parseInt(1);
 obj.siblings('.cart-item-qty').val(newAdd);
 obj.siblings('.cart-item-qty').attr('data-item-qty',newAdd);
 //$('#update-cart-item-'+iid).click();
 $('.update-cart-item').show();
 else
 if(parseInt(currentQty) > 1)
 
 var newAdd = parseInt(currentQty)-parseInt(1);
 obj.siblings('.cart-item-qty').val(newAdd); 
 obj.siblings('.cart-item-qty').attr('data-item-qty',newAdd);
 //$('#update-cart-item-'+iid).click();
 $('.update-cart-item').show();

 
 );
);
</script>

Its working fine for me.

For ajax increment and decrement quantity in minicart you can use the below extension.

https://github.com/kirtinariya1/MinicartAjaxQtyIncrementDecrement